We have

  ReservedSpace(size_t size, size_t alignment, bool large,
                         char* requested_address = NULL);

and

  ReservedSpace(size_t size, size_t alignment, bool large, bool executable);

It is way too easy to accidentally get the wrong constructor without getting a build warning. E.g. passing an "address" instead of a char* to the first variant will get me always the second variant, resulting in weird runtime errors later.

This should be less fragile.